Automatic voltage regulator



Aug. 1945- .1. HATHAWAY 2,383,309

AUTOMATIC VOLTAGE REGULATOR Filed July 30, 1941 gwa 1?, .20 i

'INVENTOR ATTOIRNEY' circuit.

For the sake of illustration, it is assumed that the screen grids I in the tube I are to be main- Patented Aug. 21, 1945 UNITED STATE AUTOMATIC VOLTAGE REGULATOR Jarrett L. Hathaway, Manhasset, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application July so, 1941, Serial No. 404,670

8 Claims.

This invention relates to automatic voltage regulators and has particularly to do with voltage regulators such as are used in speech amplifier equipment.

In many amplifiers, it is necessary to control certain voltages so that when the signals are applied, there will be no appreciable drop in the positive potentials applied to different electrodes of the amplifier tube. In power amplifiers, it has been found desirable to take special precautions tending to hold up the screen voltage. This is particularly true when amplifier tubes of the "beam power type are used.

It is an object of my invention to provide a system for automatically regulating the voltage applied to difierent electrodes of an amplifier tube. It is another object of my invention to provide a voltage regulator in association with the screen grid circuit of a signal amplifier. It is still another object of my invention to provide a convenient volumeindicator acting in association in the input circuit. Normally, the screen grid potential will be that which is obtained by a voltage divider consisting of resistors 1 and 8 across the direct current source indicated as +3 and 5 rounded -B.

The circuit diagram shows also a voltage regulator tube 9 which, in the case illustrated, may

be of the type having a common cathode, a diode.

rectifier section and a triode amplifier section.

0 A portion of the output energy derived from one side oi the push-pull amplifier is impressed across a capacitor III, a voltage divider consisting of resistive elements I I and I2, and thence to ground. Between the resistors I I and I I is a connection to one side of a capacitor I3. This capacitor couples the diverted output from the push-pull amplifier to the diode anodes It in the tube 9.

In the amplifier section of the tube 9, I show a control grid I5 connected through a resistor I6 to the diode anodes HI. The conductive path with a, voltage regulator circuit for a'power amplifier.

A combination 'diode rectifier and triode amplifier tube is preferably used in the means for voltage regulation and volume indication. As shown in the diagram, a portion of the signal is diverted from the main amplifier and applied to the rectifier section of the regulator tube. The rectified and filtered potential is then applied to the grid of the amplifier section of this regulator tube, causing its plate current to decrease with an increase in the amplitude of the signal. If this plate current decrease exactly compensates for the increased current drawn by the screen grids of the main amplifier, then the screen voltage remains constant. If desirable, the screen voltage may actually be made to rise with increase in signal amplitude by this means.

My invention will now be described in more detail, reference being madeto the accompanybetween the anodes I4 and the cathode K is conventional, being inclusive of resistors 20 and 2|.

The junction between these resistors is preferably grounded, as is the negative terminal -B of the 5 direct current source. The positive terminal of this source is indicated at +13. A by-pass condenser 22 is used to couple the grid l5 to ground. The anode I! in the tube 9 is connected through a resistor I8 to the screen grid lead for the push-.

'30 pull tubes I. In shunt with the resistor I8 is a D. C. meter I9 acting as a volume indicator and connected through a. poteniometer R2. In order to make this volume indicator read up scale in reference to the actual volume of the signal, it is connected to a bucking potential through re- .sistor R1. If desired, the relation between the total impedance of resistors I and 8 the total impedance of resistors'Ri, R2 and the space path in the triode section of the tube 9 may be adjusted 40 so that the indicator I9 will give a reading in ing drawing, the sole figure of which represents tained at a constant voltage, irrespective of the amplitude of the signals applied to the grids 6 terms of decibels of output from the amplifier tubes I. The potentiometer R2, however, is used to adjust the .zero reading of the indicator when no signal is present.

In the operation of my invention, an output component of signal energy derived from the anode of one of the amplifier tubes I traverses capacitor l0 and resistors II and I2 to ground.

Resistors II and I2 constitute a voltage divider,

and the junction between these resistors is coupled through capacitor I3 to the anodes I4. Hence, a portion of this diverted signal energy is rectified in the diode section of tube 9 and the bias on the grid I5 is thereby controlled in such a mannir that with an increase in the signal amplitude, the

grid l5 becomes more negative; consequently the triode section of tube 9 draws less current through resistor H3. The voltage on the screen grid circuit from the junctionbetween' resistors 'l and 8 on the screen grids 5 is therefore maintained at a substantially constant level, as is desired. However, the current drain in the triode section of the tube 9 may be normally maintained at a greater value than the current drain through the screen grids 5. In this case, the swing of current variations in the tube 9 may exceed that of the screen grids 5, and, in consequence, it is possible to actually increase the screen grid potential with increase in volume of the signal.

I am well aware that voltage regulators of dif- 1 'ferent types have been applied to the screen grid circuit of an amplifier but, so far as I know, such voltage regulators of the prior art do not pos ess all of the advantages which are to be derived from the system herein disclosed. Among these advantages may be mentioned the simplicity of the circuit arrangement, and its two-fold function. One of these functions is to provide voltage regullation on the screen grids; the other function is to provide a convenient volume indicator.

It is well within the scope of myinvention to provide a voltage regulator Of the type indicated which would control the D. C. potentials on any of the electrodes of an amplifier tube or tubes. Fur thermore, it will be seen that such voltage regulation maybe adjusted to obtain a steady potential or to increase or decrease the potential as a function of the signal volume. Such alternative adjustments maybe readily. obtained by those skilled in the art in view of the foregoing disclosure.

I claim: v

1. A voltage regulator for amain amplifier circuit, comprising an electron discharge device having a diode rectifier section and a triode amplifier section, a circuit for diverting a portion of the signal energy from the output side of said main amplifier circuit to be fed to said rectifier section for rectification therein, means responsive to variations in the amplitude of said signal energy so rectified for varying the control bias on the amplifier section of said discharge device, a direct current power source having connections arran ed and adapted to deliver operating potentials to said main amplifier circuit and to the amplifier section of said discharge device, said connections being such that the space path of said discharge device is in shunt with a space path portion of said main amplifier circuit across which voltage regulation is to be applied, and means controlled by the space path current in said amplifier section for effecting said voltage regulation.

2. A voltage regulator according to claim 1, and including a volume indicator in parallelwith an impedance, both being in circuit with the amplifier section of said discharge device and means for applying to said volume indicator a potential which varies in direct proportion to the output power from said'main amplifier.

3. A voltage regulator according to claim 1 and including a volume indicator so connected in series with the space path in the amplifier section of I said discharge device, so influenced thereby, and

so calibrated that it is readable in terms of decibels of amplitude of said signal energy, and is directly proportional thereto.

4. A voltage regulator according to claim 1. in which said voltage regulation is applied to a screen grid in said main amplifier circuit.

l 5. .The method of regulating the voltage applied to a screer grid with respect to the cathode of a signal-ene1 gy amplifier stage, which method comprises rectifying an output component of signal energy from said stage, producing a current drain in a conductive path which shunts the space path from the cathode to the screen grid in said amplifier, causing said current drain to be controlled in amplitude in inverse proportion to the amplitude of said rectified component of signal energy, and utilizing the variations in said current drain to maintain substantially constant the potential difference between said cathode and screen grid.

6. The method of over-compensating for voltage variations in a screen grid potential with respect to the cathode of a signal energy amplifier stage, which method comprises rectifying an output component of signal energy from said stage, producing a current drain in a conductive path which shunts the space path from the cathode to the screen grid in said amplifier, causing said current drain to be controlled in amplitude as an inverse function of the amplitude of said rectified component of signal energy, causing said current drainto exceed the screen grid current in said amplifier stage when no signal is present, and utilizing the variations in said current drain to increase the screen grid potential as a direct function of the amplitude of said signal energy.

7. The method of under-compensating for volt-' age variations in a screen grid potential with respect to the cathode of a signal energy amplifier stage, which method comprises rectifying an out potential within predetermined limits of variation.

8. In a device for regulating the screen grid potential of an amplifier in compensation for variations in the amplitude of signal input energy applied to said amplifier, fa rectifier so coupled to the output side of said amplifier as to receive a portion of the output energy therefrom, imped= ance means including a controllable electron discharge device, a source of direct current for applying operating potentials to the electrodes of said amplifier and of said device, and means for causing said screen grid potential to be upheld by a reduction of current fiow through the discharge path of said device in response to an increase in the amplitude of energy delivered by said 

